Watercraft whose means of developing dynamic lift is entirely from hydrofoils and/or planing elements develop a certain amount of drag from the structure that keeps all of these water and air foils positioned and linked. Furthermore, the performance of a hydrofoil deteriorates near the surface of the water. More extensive use of airfoil surfaces with adequate means of control and adjustment is a possible solution. Where these surfaces have a variable cant relative to the horizontal and fore and aft pivot relative to the lateral plane, trimming and controlling them to develop vertical lift or horizontal drive is analogous to trimming a windsurfer sail.
In addition to the Schweitzer/Drake windsurfer, prior art devices with which the craft of the present invention can be usefully compared and contrasted include the Amick flying boat, the Smith self-launching glider, the Magruder sailing wing and the McIntyre sailplane.
The wind-powered air/watercraft interface craft includes a fuselage or hull with a pivoting wing and tailplane, canard or secondary tandem wing and port and starboard wing tip amas, hulls, pontoons or floats of which each may have leeboards/centerboards for lateral resistance and forward or aft skegs/trim tabs/rudders, and additional sails or driving surfaces such that the wing and tail/bowplane pivot about one, two or three axes in parallel and the fuselage and leeward amas (or, in the tandem configuration, both amas) remain parallel.
The craft of the present invention, although similar in configuration to an airplane, operates in the interface between air and water, deriving both lift and drive from the relative motion of the two media. Consequently, it has more degrees of freedom in the lifting and driving surfaces and trim controls about more axes than would be necessary were the craft operating in a single medium.
The craft of the present invention is a coherent structure composed of lift and drive elements rather than a collection of lift and drive elements strung together with pure drag elements. Some of its features are found, in a comparable but different combination, in the Amick flying boat, the Smith self-launching glider, the Magruder sailing wing and the McIntyre sailplane.
In its first several embodiments, the craft of the present invention is similar in appearance to an aircraft with a high dihedral wing. In a tandem configuration it may, as does the Smith self-launching glider, include an after wing with less dihedral than the forward wing. Like the Magruder sailing wing or the Schweitzer/Drake windsurfer, wings are attached to the fuselage by a joint with one or more axes of rotation. However, the craft of the invention is different from the windsurfer in that the fuselage and wing tip amas pivot under the wings in a parallel disposition such that the roll moments generated by the wings about the fuselage or centerline center of lateral resistance may oppose each other but lift and drive forces complement each other in the configurations shown.
As in the instance of the Amick flying boat, the craft of the present invention in various embodiments is able to roll or pivot about a horizontal longitudinal axis either through the main hull centerboard(s) and center of lateral resistance or through the CLR in the leeward ama/float depending on conditions and specific dihedral of the craft. For example, with a 45xc2x0 dihedral or perpendicularly disposed port and starboard wings, the craft can rotate about the fuselage CLR, while a craft with a 30xc2x0 dihedral and maximum drive at 30xc2x0 roll about the leeward ama can be trimmed to pivot about the leeward ama CLR.
The multiplicity of possible trim adjustments could present a problem of manageability; however, it is anticipated that, for a given course of sail, some of the adjustments can be set and only a few trimmed constantly. In general, variation is through small angles and some are not precisely critical, as is the case with, for example, a keel boat heeled to 30xc2x0.
In other embodiments, the craft of the present invention resembles the McIntyre sailplane in either a catamaran or trimaran configuration. It is different in that the cross arms are lifting surfaces, the sails are wing sails and the hulls may have vertically as well as laterally lifting hydrofoil appendages.
The craft of the invention includes means for varying and/or adjusting the incidence angle of the port and starboard wings and tailplanes either together or independently relative to the horizontal plane and to the relative angle of the wind, means for varying and/or adjusting the angle of the centerline of the wing configuration relative to the-centerline of the hulls, and means for varying the angle of the wing configuration relative to the vertical, and for varying the incidence angle of the tailplane relative to and independently of that of the main wing configuration.
The craft of the invention may include articulation of any of the wing surfaces in a chordwise direction, so as to vary the surface""s lift coefficient independently of its angle of incidence.
Wings to pivot as described are mounted on an axis perpendicular the datum waterline (DWL) of the main (center) hull, a transverse spanwise axis and a longitudinal horizontal axis (which may be the fuselage itself).
On any of the embodiments, wings can be rotated or parallelograms of wings and amas can be skewed by a variety of means or combination of means such as: drum winches and cables, operated manually or by servo motors, or tillers, or steering gears with wheel or joystick or servo motor operation. Similarly, wings can be trimmed about their spanwise axes by a variety of means or combination of means. With the single wing or wing and bow or tailplane configuration, it may be preferable to have each ama pivot about a single axis perpendicular to the plane defined by the chordline and spanwise axis of the wing.
In some embodiments, wings may be mounted on pylons above the fuselage so as to lower the payload and center of gravity of the craft and improve its transverse stability. The length (height) of the pylons may be varied by mechanical means. The weight of the fuselage may be varied by flooding or emptying of water tanks.
Angles of attack of vertically or horizontally lifting hydrofoil surfaces may be varied and foils may be retracted or adjusted in area or extended as the craft fuselage and/or amas are lifted clear of the water""s surface. The angle variations are essential in enabling the wings to drive the craft as a sailing boat and provide vertical lift to allow the fuselage to fly clear of the water""s surface with only minimal ama and lateral resistance in the water.
Hydrofoils/leeboards/centerboards on the fuselage/amas may also be curved or hooked so as to provide optimum horizontal and vertical lift for the given conditions. They may also be compound foils angled or configured to generate lateral and/or vertical force as needed.
Port and starboard wing/tailplanes/bowplanes may have dihedral angles relative to the horizontal of between 0xc2x0 and 45xc2x0, but the dihedral angles of the main wing and the secondary wing/plane do not necessarily have to be the same. The wing dihedral angle of a given craft may be variable by mechanical means for different wind conditions.
The craft may also be designed without the tail/bow plane or secondary wing so that balance and steering are accomplished by trim and pivoting of a single wing. The craft may also have more than two or a multiplicity of port and starboard wing/tail/bow plane/elements.
The wing configuration may also be used in conjunction with wheels for land sailing or ice runners instead of hulls and amas. The port and starboard wing spans may also have a secondary inflection point giving them a double dihedral angle with the amas mounted at those secondary inflection points. A double dihedral would limit the roll angle but might have some structural benefits. The angle between the vertical windward span and the leeward span defines the maximum roll angle.
The craft may have an auxiliary motor with an air propeller to facilitate free flight and or fuselage lift-off.
The craft may be any size from a small scale model, self-tending and/or radio controlled, to a payload or multiple passenger carrying version. The choice of materials will be determined by the size and function of the craft and vice versa. It can be built using aircraft or light weight marine construction techniques in wood, various composites or aluminum. Wings/sails may also consist of some sort of framework with a fabric skin and/or inflatable elements.
The craft may have a gimbaled cockpit or fuselage, or the wing assembly may be mounted on a hinge or cylinder that encircles and rotates about the longitudinal axis of the fuselage so that the fuselage remains upright as the wings rotate from one tack to another.
In embodiments which have high dihedral wings, a compression strut may link the port and starboard wing tips of the craft, to help preserve the angular relationships under load, and provide for varying the dihedral of the wings.
In some embodiments, the craft of the invention may have wings of small, 0xc2x0, or negative dihedral angle and canted, symmetrical and articulated or flexible wingsails projecting from each of the two amas and optionally connected by a central xe2x80x9cbridgexe2x80x9d or double pivot for rigidity. The wingsails are angled so that the capsizing moment produced by the parallel driving forces is opposed by an equal righting moment developed by the vertical force vectors. It may also consist of a catamaran craft with amas and the above mentioned symmetrical sails but no central fuselage.
In a preferred embodiment, the catamaran would be similar to the McIntyre sailplane developed by Elco Works, except that it would have aero and/or hydro lifting surfaces in addition to buoyancy and dynamic lift developed by the hulls. In a heavy displacement configuration, the twin hulls could be fixed in relation to each other, and the rig/wingsails could pivot in the same parallelogram disposition by means of the bases of the wingsails moving on tracks that would follow the locus of corners of a skewable parallelogram on the deck of the craft.
Further variations include any of the above mentioned small dihedral craft with tandem or multiple driving wingsail systems. The after xe2x80x9csailsxe2x80x9d in the tandem craft would be slightly higher than the forward ones to avoid downwash from the forward wings. Successive wings would resemble a xe2x80x9ctelescopingxe2x80x9d of the triangles. Because of the dynamic stability of the system, it could have commercial as well as recreational applications. The possibility of furling or retracting fabric or inflatable wing sails or a rig that could be lowered altogether further enhances its seaworthiness.
Any of the aforementioned craft could use sensors, similar to Christopher Hook""s or Greg Ketterman""s forward ski sensors, ahead of the hulls to adjust trim angle of all vertical lifting surfaces with wave motion of the water surface.
A triangle rig may also be used as a method of propulsion for a wide beam single hull ship such as, for example, a 200,000 dwt or larger VLCC. In this embodiment of the present invention, there is no need to be limited by the complication and expense of including means for skewing the rig. In this embodiment, the triangle configuration wing sails are mounted in tandem in a fixed (non-skewing) arrangement to the port and starboard rails or outer shell of a single hull ship. Preferably, a platform is provided at the top of the rig for use appropriate to the ship""s requirements.
The opposed canted wing sails and center of effort that is very low in proportion to the length of the vessel will keep the heeling moment to a minimum. It is intended for vessels operating at speed/length ratios of less than 0.5, that is, large (700 ft.-1300 ft. in length), low speed (under about 17 knots) vessels. Sail propulsion for these ships therefore acts as an auxiliary to the ships engines, and the size of the rig is small in relation to length of the ship. Also, the height of the rig may be limited by bridge heights in places such as the Verrazano Narrows. In average true wind speeds of, say, 25 knots, large ships, with an operating speed range of around 15 knots, will have an apparent wind angle forward of the beam on most points of sail. Consequently, wing sails are appropriate for these vessels.
Because the ship is under-rigged in the conventional sense, the side force generated by the sails will be small in proportion to the opposing side force generated by the hull canoe body. Consequently, the lateral plane of the flat sided hull will provide adequate side force for windward performance. The center of lateral plane of such a craft will vary in a manner that its precise location in relation to the rig is neither critical nor controllable, so that the adjustment of the longitudinal center of effort of the rig by skewing is not important.
The driving (lifting) surfaces are also small in proportion to the major aerodynamic drag elements on the vessel, namely the superstructure and the standing rigging. It is important, therefore, to minimize that aerodynamic drag by fairing the superstructure and streamlining the rigging.
Platforms at the top of each of the rigs are preferably provided for mounting swiveling wind turbines and/or cranes for cargo handling. The platforms may also be used to mount other mechanisms or structures such as control mechanisms, a crow""s nest or an observation platform, for example. The turbines can be used to directly or indirectly power the ship""s main plant and may drive underwater propellers through a flexible hydraulic drive or generate electric power transmitted to the ship by cables led inside the masts. Smaller secondary turbines aft of the primary ones can, with proper ducting, develop power from the vortices off the tips of the wing sails.
Primary trim will be variation of angle of attack about the spanwise axes. Adjusting camber to correspond to the direction of aerodynamic lift is a secondary consideration. There are numerous possible arrangements for varying the camber of these initially symmetrical chord foils and for retracting them, furling them or in any way xe2x80x9cshortening sailxe2x80x9d.
The specific choice of material and mechanical system for camber variation will depend on the precise wing section and the extreme conditions to which it is designed. It will also depend on cost versus fuel savings, and safety and durability considerations. A wing sail composed of rigid sections would avoid some of the control, fatigue and safety problems due to flutter inherent in a flexible fabric sail. Feathering the wings may produce less wind resistance and negative force than a xe2x80x9cbare polexe2x80x9d or unstreamlined though smaller profile.
The principles of the invention will be further discussed with reference to the drawings wherein preferred embodiments are shown. The specifics illustrated in the drawings are intended to exemplify, rather than limit, aspects of the invention as defined in the claims.